What are the common problems in plastic mold processing?

Too low or too high back pressure in injection molding will affect product quality. When the back pressure is too low, the screw retreats too fast, and the density of molten material flowing into the front end of the barrel is low, which leads to poor plasticizing quality, unstable injection quantity and great changes in product weight and size. There will be some bad phenomena on the surface of the product, such as shrinkage, hollowing, cold particles, uneven luster and so on. In addition, bubbles are easy to appear inside the product, and glue is easy to come out around the product and at the bone position; The back pressure is too high, the melt pressure at the front end of the barrel is too high, the material temperature is high, the viscosity decreases, the reverse flow of the melt in the screw groove and the leakage between the barrel and the screw increase, and the plasticizing efficiency decreases. For plastics (such as PVC and POM) or colorants with poor thermal stability, the increase of melt temperature and heating time in the barrel will lead to thermal decomposition, or the discoloration degree of colorants will increase, and the surface color/luster of products will become worse. The back pressure is too high, the screw returns slowly, the preform return time is long, the cycle time is increased, and the production efficiency is reduced. High back pressure and high melt pressure. After glue injection, the nozzle is easy to melt and drool. The next time the glue is injected, the cold material in the nozzle channel will block the nozzle or make the product appear cold material spots. In the injection process of plastic mold, the nozzle often leaks glue due to excessive back pressure, which causes waste of raw materials and burns out the heating ring near the nozzle.